1. Institute of Food Chemistry, University of Muenster, Corrensstrasse 45, D-48149 Münster, Germany; German Research Center for Food Chemistry, Lichtenbergstrasse 4, D-85748 Garching, Germany; and Chair of Food Chemistry and Molecular Sensory Science, Technical University of Munich, Lise-Meitner-Strasse 34, D-85354 Freising, Germany